Dictionary

milmillonésimo

/milmiʝoˈnesimo/

adjective/milmiʝoˈnesimo/

billionth

“la milmillonésima persona” — the billionth person

noun, masculine/milmiʝoˈnesimo/plural: milmillonésimos

milmillonésimo is masculine in Spanish.

billionth (1000 000 000.°)

“tres milmillonésimos” — three billionths (³⁄_(1,000,000,000))